Device for establishing high pressure and temperature

ABSTRACT

Two dies interconnected along the periphery thereof are provided on their oppositely adjacent face surfaces with center recesses and ridges, the latter being disposed coaxially in relation to said recesses. When the dies are drawn together said recesses are adapted to form a high pressure chamber in which a container made of a thermal and electrical insulating material which is ductile under omnidirectional compression is enclosed whereas the ridges are adapted to form concentric circular compartments with the clearances in the joints thereof successively increasing towards the periphery of the dies. The volumes of said compartments also increase from the center towards the periphery of the dies. These compartments are locking in their function and ensure a smooth reduction of pressure exerted by the ductile material on the face surfaces toward the periphery of the dies.

United States Patent [1 1 Sirota et al.

Feb. 5, 1974 [76] Inventors: Nikolai Nikolaevich Sirota,

Leningradsky prospekt, 78, korpus 1a, kv. 141, Moscow; Anatoly Mitrofanovich Mazurenko, ulitsa Vostochnaya, 25, kv. 53; Nikolai Alexeevich Strukov, Leninsky prospekt, 44, kv. 162, both of Minsk, all of USSR [22] Filed: July 14, 1972 21 Appl. No.: 271,650

[52] US. Cl 425/77, 425/406, 425/D1G. 26

[51] Int. Cl B30b 11/32 [58] Field of Search 425/406, 77, DIG. 26

[56] References Cited I UNITED STATES PATENTS- 2,94l,242 6/1960 3 Hall 425/77 2,941,243 6/1960 Bundy 425/77 2,941,244 6/1960 Wentorf, Jr 425/77 3,268,951 8/1966 Newhall 425/77 3,695,797 10/1972 Bakul et al 425/77 3,732,043 5/1973 Bakul et al 425/77 Primary Examiner-Robert L. Spicer, Jr. Attorney, Agent, or Firm-John C. Holman et a].

57 ABSTRACT Two dies interconnected along the periphery thereof are provided on their oppositely adjacent face surfaces with center recesses and ridges, the latter being disposed coaxially in relation to said recesses. When the dies are drawn together said recesses are adapted to form a high pressure chamber in which a container .made of a thermal and electrical insulating material 2 which is ductile under omnidirectional compression is enclosed whereas the ridges are adapted to form concentric circular compartments with the clearances in the joints thereof successively increasing vtowards the periphery of the dies. The volumes of said compartments also increase from the center towards the periphery of the dies. These compartments are locking in their function and ensure a smooth reduction of pressure exerted by the ductile material on the face surfaces toward the periphery of the dies.

5 Claims, 5 Drawing Figures llllllllllumnm pumnmullllllllIll iii - PAIENIEDFEB 519M SHEET 1 OF 2 In? N Jnmuiiiii DEVICE FOR ESTABLISHING HIGH PRESSURE AND TEMPERATURE BACKGROUND OF THE INVENTION The present invention relates generally to devices for establishing high pressure and temperature and more specifically, it relates to devices for synthesizing super- .hard materials, such as diamond and cubic boron niber into a slot formed between the dies and is reduced as the dies are drawn closer together. Forces of friction increasing between pyrophyllite and the tapered surfaces of the dies made of a hard alloy ensures compressing the container with the reactive compound in the chamber up to a pressure of about 35 kilobar. Application of lithographic stone as a material of the container permits the pressure in the chamber to rise to more than 60 kilobar.

A disadvantage of this device lies with the instability of pressure inside the chamber at repeated use of this device for synthesizing superhard materials. This is due to the fact that stresses (pressures) exerted on the tapered surface of the dies during the compression of the container material are actually non-uniform.

The concentration of stresses on the edges of the recesses and the effect of high temperature lead to plastic deformation of said edges; the profile of the dies in the diametrical cross-section is susceptible to variation in the course of multiple repeated load, and as a result, the pressure inside the chamber under the equal force exerted by the press in every attempt of synthesizing, will invariably be altered under no controlled conditions.

The temperature that can be achieved with this device is approximately 2,000C which is not always sufficient for the process of synthesizing. Upon increasing the temperature in the chamber beyond the above limit, the force of friction generated between the container material and the tapered surfaces becomes inadequate to restrain the pressure inside the chamber. Furthermore, this device of the prior artis devoid of any electricalinlet into the pressure chamber, which makes it more difficult to exercise accurate control and sustain the synthesis temperature as for example by means of a thermocouple. The introduction of a thermocouple through the slot formed between the faces of the dies does not yield good results as the thermocouple is actually sheared-off in the joint made up by the edges of the recesses in the dies, which is caused by a non-uniform distribution of pressure over the working surface of the dies.

Also known in the art is a device taught in US. Pat. No. 3,695,797 in the names of V. N. Bakul and others, wherein the oppositely adjacent faces of the dies incorporate circular ridges coaxial in relation to center recesses and disposed across a diameter equal to 1.3-1.5 of the recess diameter of the dies. A container in this device is provided with an external rubber ring which, in the course of the dies being drawn together, fills-in the slot between the surfaces of the ridges and forms a gasket which puts up hydraulic resistance to lithographic stone being displaced from the chamber. The above device makes it possible to stabilize to a certain degree the pressure inside the chamber and somewhat reduces the deformation of the recess edges in the course of multiple repeated use of the device for diamond synthesizing. However, the rubber-made circular gasket is of low efficiency at temperatures between 2,000-3,000C in the chamber as is in the case of synthesizing cubic boron nitride. This is because thetemperature of the die surface'materially exceeds the thermal stability limit of rubber,

SUMMARY OF THE INVENTION It is therefore an object of the present invention to increase the functional reliability of the device for establishing high pressure and temperature within the range of obtainable pressures and temperatures needed for synthesizing diamond and cubic boron nitride.

It is further object of the present invention to develop a device which provides for the reestablishment and stability of pressure under the constant force exerted by a press in the course of multiple applications of said device for the synthesizing process within a wide range of pressures and temperatures.

It is a still further object of the present invention to prolong the service life of a device for establishing high pressure in large reactive volumes.

his one more object of the present invention to provide a device for establishing high pressure and temperature, which allows a thermocouple to be introduced into the pressure chamber.

It is yet another object of the present invention to develop a device for establishing high pressure and temperature which can be made of steel without the use of hard alloy.

These and other objects are achieved by the provision of a device for establishing high pressure and temperature, comprising two identical dies interconnected along the periphery and having circular ridges on oppositely adjacent faces, said ridges being disposed coaxially in relation to center recesses forming a high pressure chamber when said dies are being drawn together, said chamber incorporating a container, made of a thermal and electric insulating material which is ductile under omnidirectional compression, wherein according to the invention, the ridges are so arranged that the oppositely adjacent faces of the dies are given a serrated profile in the diametrical cross-section and when the dies being drawn together they form concentric circular compartments which are filled in during compression with the container material, whereas the clearances in the joints of said compartments are successively increasing towards the periphery of the dies, while the volume capacities of said compartments are so defined that at a given pressure in the chamber a gradually reduced pressure is ensured of the container material as exerted on the face surfaces towards the periphery of the dies.

An advantage of the present invention is that the pressure in the concentric circular compartments formed by the die faces when the latter are drawn together, is gradually reduced from the center recess towards the periphery. This result causes the edges of the recesses in the dies to undergo the effect of pressures close to omnidirectional, thus preventing deformation of said edges in the course of multiple use of the device in the process of synthesizing. The smooth reduction of pressure in the compartments takes place because individual pressure in each of said compartments originated when the dies are drawn together, offers counterpressure or resistance to the container material being displaced from a preceding compartment, i.e., each of the compartments adds to enhance the locking ability of the preceding compartment. Therefore, the compressing stroke of the device is enlarged to allow a possible increase'of the working volume of the chamber or a widening of the pressure range achieved.

The locking ability of the device as a whole increases as against a device comprising the dies 'with plain tapered surfaces and this gives a possibility to widen the temperature range of the device to the limit of 3,000C. For a temperature in the chamber between l,300-1 ,500C, the device employed can be made of steel alone. A device, according to the present invention provides for gradual redistribution of the container material amongthe compartments and, thereby, ensures smooth redistribution of pressure in the course of the dies being drawn together. One more advantage of the present invention is a better production technology of the dies by the method of powder metallurgy.

It is expedient that the volumes of compartments will be successively increasing from the center recess towards the periphery of the dies.

According to the present invention, the consecutive apices of the ridges can be disposed on a common tapered surface.

In another embodiment of the present invention, the apices of the ridges which are closer to the periphery of the dies are disposed on a tapered surface inclined at a lesser angle to the longitudinal axis of the center recess than the tapered surface on which the apices of ridges are disposed to form clearances successively increasing toward the periphery.

It is expedient that the ridge apices are made rounded.

BRIEF DESCRIPTION OF THE DRAWINGS The detailed construction of the present invention is described hereinafter for which reference is made to the accompanying drawings, in which:

FIG. 1 is a diametrical sectional view of a device for establishing high pressure and temperature constructed according to the present invention and shown in a position prior to compressing the container:

FIG. 2 is the structure as shown in FIG. 1 upon compressing the container;

FIG. 3 is a diametrical sectional view of a device for establishing high pressure and temperature, according to the present invention, which is intended for developing pressure in high volumes;

FIG. 4 is one of the ridges on the serrated surface; and t FIG. 5 is a diametrical sectional view of a device for establishing high pressure and temperature, constructed according to the present invention, with an 4 electric inlet into the compression chamber (prior to compression).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The device comprises two identically shaped and dimensioned dies 1 (FIG. 1) with center recesses forming together a chamber and a container 2 made of a thermal and electric insulating material, which is such as lithographic stone, ductile under omnidirectional compression and filled .with reactive compound 3. The reactive compound can be also enclosed in a tubular graphite-made heater of a conventional type. The oppositely adjacent faces of the dies carry ridges 4 which impart to said surfaces a serrated profile in the diametrical cross section. Apexes 5 of the ridges 4 are disposed on a common tapered surface with the apex of the latter surface lying on a line through the centers of curvature of the recesses in the dies 1. The dies 1 are fitted with fixing rings6.

Then the dies 1 (FIG. 2) are drawn together, concentric circular compartments 7, 8 and 9 are formed between the faces of dies. The compartments are, filled with the material of a container 2 in the course of the dies being drawn together. The container 2 (FIG. 1) is provided'with a fan-shaped shoulder 10 which in the initial position (prior to compression) fills, partially or fully, the space of a compartment 7 being the closest to the recesses. I I

The cubical volume of the container 2 should be of a value ensuring complete filling of the entire spacebetween the faces of dies 1 with lithographic stone of the container 2 when in the final position (upon compres sion of the device by a press). In this 'case, a smooth reduction of pressure is achieved from the center toward the periphery along the working surface of the dies. Compartments 7, 8 and .9 represent a successive line of spaces wherein pressures P-,, P, and P. are gradually reduced. This is obtained because the values of clearances in the joints of sections, i.e. between the apices of the ridges, are successively increasing toward the periphery of the dies and consequently the locking ability of each of the clearances is successively reduced thefarther they lie from the center recess of the dies 1.

Furthermore, when the dies 1 are drawn together, a time interval occurs between the moments of initiating the compression of lithographic stone in compartments 7, 8 and 9, inasmuch as the filling of the subsequent compartments takes place only upon complete filling of the preceding compartments with the container material. Because of the gradual reduction of pressure along the surface of the dies 1, a most vulnerable point of the device, that is the edge of the center recess, is actually found under the conditions of undergoing the omnidirectional pressure which precludes a possibility of altering the profile shape of the dies 1 By varying the taper angle of the surface carrying the apices 5 of the ridges 4 and the taper of the ridges 4 proper and also by observing the requirement that the volumes of locking compartments 7, 8 and 9 are successively increasing the farther they liefrom the center recess of the dies 1, it is possible to attain the desirable distribution of pressure over the working surface of the dies 1. At

lesser taper angles of the surface carrying the apices 5 of the ridges4, a smoother pressure reduction can be attained in proportion to the distance from the center recess of the die 1, while the locking ability of the successive line of compartments as a whole will be higher. In this case, a stable temperature of 3,000C and higher can be attained in the chamber, whereas the pressure in the chamber is increasing non-linear in relation to the force applied by a press and the efficiency of the device will be lower than the efficiency of the device with a larger taper angle-of the surface carrying the apexes 5 of the ridges 4. However, the locking ability of the compartments as a whole will be in the latter case correspondingly lower. Therefore, the values of said angles are determined by a task which is set forth and can be chosen within the limits of about 3-4 to about 68. The locking ability of the compartments of the device-can be increased with the retention of a higher efficiency by disposing the apices of the ridge 1 1 (FIG. 3) which is the closest to the die periphery, on a tapered surface inclined to the longitudinal axis of the center recess at lesser angle 04 than angle B of the taper of the surface carrying the apices of ridges 4 which form the clearances successively increasing towards the periphery. This embodiment of the device is the preferable embodiment for establishing pressure in high volume capacity chambers.

I The device functions as follows. When the dies 1 under the action of a press are drawn together, compression of the container is initiated and the pressure inside the chamber is increased. The material of the container 2, as the process goes on, is partially displaced from the chamber and fills at first the innermost concentric circular compartment 7. As the dies 1 continue being drawn closer together and simultaneously with compressing lithographic stone in the chamber and in the first inner compartment, filling is initiated in an adjacent compartment 8 with the further displaced material of the container and so on. until all the compartments are fully filled. Each of the clearances formed by a pair of opposite ridges, as the dies are drawn closer together, will put up an increasing resistanceto the material of the container 3 being displaced from the compartment. Since each compartment prior to commencing the displacement of lithographic stone therefrom, has a certain initial pressure, the displacement of the material into each subsequent compartment, as well as thedisplacement of the material from the chamber, will take place by shifting the middle layers in relation to stationary layers or those as in the given case, which contact the surface of the dies 1. As is known, the shearing strength of the material, especially of lithographic stone, quickly rises with the increase of pressure. All this ensures an increasing compressing stroke and at the same. time widens the range of attainable pressures, or permits a larger working volume of the device to'be obtained.

Rounding of apices and grooves of the ridges, as shown in FIG. 4, contributes to a more uniform redistribution of lithographic stone, and also that of pressure among the compartments as the dies are drawn together, prevents concentration of local stresses on the surface of the dies and permits a better technology of manufacturing the dies by the method of powder metallurgy.

The practical proof of the smooth distribution of pressure created by the container material, along the surface as of the dies and in the given case, is achieved by introducing a thermocouple l2 and 13 and other measuring probes into the pressure chamber directly through the clearance between the dies, as can be seen in FIG. 5. Shearing-off a thermocouple which can be observed at the very beginning of compression when the dies are made with an even bevelled working surface will not take place in the device constructed according to the present invention until a pressure is reached of at least -80 kilobars.

Electric power for heating the reactive compound or a tubular heater is supplied through the dies and at least one of them should be electrically insulated from a press.

In the device according to the invention, the geometry of the working surface of the dies provides an efficient backup to the most heavily stressed sections of the surface thereof and a reliable locking of the chamber, the geometry permitting the use of steel as a construction material for dies. The applicability limits of the device are determined in the given case only by temperature conditions. In practice, this device made of steel can be employed 'for synthesizing diamonds.

What we claim 'is: n

1. A device for establishing high pressure and temperature, comprising two identical dies interconnected along the periphery thereof and provided on the oppositely adjacent face surfaces thereof with center recesses and a plurality of ridges, said ridges being disposed coaxially to said center recesses, said ridges being so arranged that said faces have in a diametrical cross section a serrated profile, whereas when said dies are drawn together said ridges are adapted to form concenof said compartments are so defined that at a given pressure in a chamber a smooth reduction of pressure is ensured, exerted by a ductile material on the face surfaces towards the periphery of said dies, said recesses when said dies are drawn mutually together forming a high pressure chamber; a container of a thermal and electrically insulating material which is ductile under omnidirectional pressure being enclosed in said chamber. i

2. A device as claimed in claim 1, wherein the volumes of said compartments are successively increasing from said center recess towards the periphery of said dies. i

3. A device as claimed in claim 1, wherein the subsequent apices of said ridges are disposed on a common tapered surface. t

4. A device as claimed in claim 1, wherein the apices of said ridges-closest to the periphery of said dies are disposed on a tapered surface inclined to the longitudinal axis of said chamber at a lesser angle than a tapered surface carrying the apices of said ridges forming clearances increasing toward the periphery.

5. A device as claimed in claim 1, wherein said apices 

1. A device for establishing high pressure and temperature, comprising two identical dies interconnected along the periphery thereof and provided on the oppositely adjacent face surfaces thereof with center recesses and a plurality of ridges, said ridges being disposed coaxially to said center recesses, said ridges being so arranged that said faces have in a diametrical cross section a serrated profile, whereas when said dies are drawn toGether said ridges are adapted to form concentric circular locking compartments, the clearances in the joints of said compartments successively increasing towards the periphery of said dies, wherein the volumes of said compartments are so defined that at a given pressure in a chamber a smooth reduction of pressure is ensured, exerted by a ductile material on the face surfaces towards the periphery of said dies, said recesses when said dies are drawn mutually together forming a high pressure chamber; a container of a thermal and electrically insulating material which is ductile under omnidirectional pressure being enclosed in said chamber.
 2. A device as claimed in claim 1, wherein the volumes of said compartments are successively increasing from said center recess towards the periphery of said dies.
 3. A device as claimed in claim 1, wherein the subsequent apices of said ridges are disposed on a common tapered surface.
 4. A device as claimed in claim 1, wherein the apices of said ridges closest to the periphery of said dies are disposed on a tapered surface inclined to the longitudinal axis of said chamber at a lesser angle than a tapered surface carrying the apices of said ridges forming clearances increasing toward the periphery.
 5. A device as claimed in claim 1, wherein said apices and depressions of said ridges are rounded. 